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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Polymer bulletin 36 (1996), S. 391-398 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary We have synthesized a polyacetylene derivative, poly(dipropargyl-16-crown-5), through the cyclopolymerization of the corresponding monomer by metathesis catalysts. The polymer containing crown-ether units was characterized by spectroscopic and thermal techniques. The polymer structure is believed to be a cyclized from with both five- and sixmembered rings. The polymer exhibits high cation-binding properties and ionochromic effects. The order of the selectivity of alkali- metal cations for both the monomer and the polymer was found to be Na+〉K+〉Li+ and the polymer shows the largest red shift by approximately 40 nm in λmax for Na+.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of applied electrochemistry 23 (1993), S. 1031-1038 
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Electrodeposited polyaniline (PANT) in the emeraldine oxidation state was used as the electrodes of open rechargeable cells containing 1 m HClO4 as the electrolyte. The cells could be charged at very high hourly rates to 85% of the redox charge in the leucoemeraldine-emeraldine transition of the polymer. Contrary to normal behaviour of rechargeable cells, the coulombic efficiency improved with increasing rates of charge injection and withdrawal. This is attributed to less charge being dissipated by self-discharge at high rates of discharge. The poor charge retention was caused by reactions between the charged electrodes and their environment. The decrease in cell voltage on standing may also be induced by internal redox reactions of PANT of different oxidation states present at the electrodes as a result of incomplete oxidation or reduction during cell operation. Ultraviolet (u.v.) spectroscopy of the charged electrodes identified mostly protonated leucoemeraldine at the negative electrode and pernigraniline at the positive electrode. The irreversibility in the oxidation from the emeraldine state to the pernigraniline state accounts mostly for the degeneration of cell performance after prolonged cycling.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of applied electrochemistry 22 (1992), S. 512-516 
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The charge-discharge characteristics of polyaniline (PAn)-Nafion®-PAn composite films used as rechargeable batteries were investigated. The batteries were formed chemically by sandwiching Nafion® between two thin layers of PAn-Nafion® composite in equilibrium with various electrolytes. It was found that cells with LiClO4 in propylene carbonate as electrolyte showed the highest capacity. The charge and discharge performance of the battery was almost independent of the choice of anions but was significantly affected by cation size. This may indicate that the insertion or removal of charge-compensating electrolyte cations from the composite layer was responsible for the redox of PAn during the charge and discharge cycles.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of applied electrochemistry 22 (1992), S. 738-742 
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Thin films of polypyrrole (PPy) and polyaniline (PANi) were electrochemically deposited on stainless steel substrate under potentiostatic control. Secondary batteries were assembled using these polymers as active electrode materials and propylene carbonate (PC) solutions of tetraethyl ammonium perchlorate (TEAP) as the electrolyte. In repeated charge and discharge tests, the all PANi cells performed better than the PPy-PANi cells in voltage characteristics, recyclability, charge retention and coulombic efficiency. There appears to be an optimum charging current for the polymer cells and charging the cells at rates notably different from the optimum value reduced the cell performance substantially. It is suggested that the cells operate under kinetic control and charging at extreme rates either reduces the participation of polymer redox in the overall cell operation or produces mass transfer limitations.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 53 (1991), S. 279-281 
    ISSN: 1432-0649
    Keywords: 42.65 ; 72.40 ; 78.65
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Photoconductivity measurements on a stable photocrosslinkable nonlinear optical polymer — PVCN (polyvinylcinnamate)/CNNB-R (3-cinnamoyloxy-4-[4-N,N-diethylamino)-2-cinnamoyloxy phenylazo] nitrobenzene) are reported. Photoconductivity in this polymer system, in both crosslinked and uncrosslinked states, was observed without introducing any sensitizer or carrier-transport agents. Absorption of CNNB-R (λpeak=518 nm) results in photocarrier generation and it is conjectured that CNNB-R also plays a role in the carrier transport. Such polymers are candidate materials for photorefraction.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    The international journal of advanced manufacturing technology 15 (1999), S. 38-48 
    ISSN: 1433-3015
    Keywords: Key words.Alternative interpretation; Feature-based design; Feature extraction; STEP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: One of the major difficulties in extracting machining features is the lack of a systematic methodology to generate alternative ways of manufacturing a machined part. Most of the early research in feature extraction and process planning has not considered this aspect, and has focused on the generation of a single interpretation. In this paper, we propose a feature-based approach to generating alternative interpretations of machining features from a feature-based design model. The proposed approach simplifies the generation of alternative machining feature models by using information on feature which is captured and maintained during feature-based model-ling and machining feature extraction. A set of machining features is incrementally extracted during the feature-based design process of a machined part. A feature conversion process converts each design feature into a machining feature or a set of machining features by using information on the geometry and the feature. Using reorientation, reduction, and/or splitting operations, alternative models are generated from the sets of extracted machining features. During the execution of each operation, unpromising models are pruned by using criteria such as minimising the number of accessibility directions. The machining features and their precedence relationships are represented in a STEP-based machining feature graph for the purpose of data exchange.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Environmental monitoring and assessment 19 (1991), S. 131-138 
    ISSN: 1573-2959
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Mixed metal oxides are discussed as possible substitutes for noble metals in automobile catalytic converters. The catalytic activity for CO oxidation of LaMnO3 and La0.5Sr0.5MnO3 catalysts was examined. The ability of these catalysts to provide lattice oxygen and to sustain the oxidation reaction, even in the absence of molecular oxygen, has been confirmed. Measurements were performed of the reversible oxygen uptake on the two catalysts.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 21 (1986), S. 346-354 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The hydriding kinetics of an Mg2Ni alloy are investigated under hydrogen pressures from 2.5 to 8 bar (0.25 to 0.8 MPa) at various temperatures (543 ⩽T ⩽ 583 K). The hydriding reaction of Mg2Ni progresses by a nucleation and growth mechanism. The rate-controlling step is analysed to be the forced flow of hydrogen molecules through pores, interparticle channels or cracks of the sample, involving heat-transfer control.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 21 (1986), S. 2430-2434 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The solid-liquid diffusion couple technique was employed to determine the interdiffusion coefficient of the gamma phase in the Ag-Hg contact reaction. Diffusion coefficients were calculated with the aid of an equation given by Wagner. The composition range of the gamma phase was determined to be between 55.3 and 57.5 at% by electron microprobe analysis, and values for the average interdiffusion coefficient of the gamma phase were found to beD av(cm2sec−1)=3.181×10−5exp (−32539 (J mol−1)/RT) in the temperature range 40 to 115° C. The amalgamation reaction between silver and liquid mercury proceeded with the formation of gamma phase and a solid solution of Ag-Hg. The growth of gamma phase followed a parabolic rate law. The penetration of liquid mercury into grain boundary of the gamma phase caused the gamma to be crumbled off. The possibility of short-circuit diffusion is discussed.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 22 (1987), S. 3949-3955 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Model experiments to explore the amalgation mechanism in conventional Ag3Sn and high copper single-composition dental alloys have been conducted by rotating alloy roda in liquid mercury at different speeds and for different durations. After removing the rod from the mercury, the vacuum volatilization technique was used to accelerate the supersaturation of dissolved elements in the liquid mercury. The surface and sectional scanning electron microscope (SEM) views give direct evidence for new amalgamation mechanism in high copper dental alloys. The amalgamation reaction begins with the selective dissolution of the Ag3Sn phase in mercury, tin gettering to the crumbled-off Cu3Sn phase, heterogeneous nucleation of the Cu6Sn5 phase on the seed of the crumbled-off Cu3Sn phase and was followed by the nucleation of the Ag2Hg3 phase. The unexplained phenomena, the formation of the γ-2 phase (Sn7-8Hg) in higher content of mercury and the nonexistence of the γ-2 phase in higher content of copper alloys such as Sybralloy, were clearly understood by applying the new model.
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